Polyunsaturated fatty acid (PUFA) percentage was found to lift 25 per cent on grass diets, although due to overall fat content being higher in grain-fed beef, PUFA in steak was greater in grain finished cattle.

Dr Hicks demanded more research be done to tie up remaining loose ends, adding that studies on global or European systems are not relevant for US beef.

Varieties in breed and forage variety/form are the main complicating factors, he added.

And while no concrete conclusions could be drawn on the merits of grass or grain, a study by a leading US beef company could have found the perfect sized carcass.

Yield grade three was optimum for returns per grain-fed beef animal in 2013, a study by US Premium Beef LLC has found.

Disregarding cattle fed Zilpaterol, the study found that carcass price/hundredweight and dollars per carass were:

YG1 $193.75 and $1609

YG2 $197.94 and $1684

YG3 $201.04 and $1762

YG4 $196.98 and $1783

YG5 $189.45 and $1770

Yield grade four and five have a slightly higher total return but tended to be fatter carcasses, meaning less efficient with feed during finishing, the paper concluded.

Michael PriestleyNews Team - Editor

Mainly production and market stories on ruminants sector. Works closely with sustainability consultants at FAI Farms